LABORATORY ACTIVITIES FOR REGENTS CHEMISTRY

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LABORATORY ACTIVITIES FOR REGENTS CHEMISTRY
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Many laboratory activities require
measurements. Science uses the S.I. (Metric
System) of measurements.
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Types of measurements

• Linear (length or distance)
• Mass (weight)
• Volume
• Temperature

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All measuring instruments have calibrations.
These are the markings or divisions on the
measuring tool.
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Linear measurements are made using a Meter Stick
or Metric Ruler.
Metric Ruler
Meter Stick
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The basic unit for linear measurement is the
meter (m.). Other commonly used units are the
centimeter (cm.) and millimeter (mm.). One
advantage of the metric system is that everything
is based on the number, 10, or some multiple of
10. 10 mm. 1 cm. (and 1 mm. 0.1 cm.)
100 cm. 1 m. (and 1 cm. 0.01 m.)
Also, 1000 m. 1 kilogram (kg.).
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cm. marks
mm. marks
A metric ruler
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When making measurements, scientists use a
concept and a practice known as significant
figures (Sig. Figs.)
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Significant figures include an estimated digit
that is always one place beyond the calibrations
on any measuring instrument.
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Estimating the last digit in a measurement
You might estimate the end of the cylinder to be
half-way between the lines or 0.05 cm. This digit
must be included in the measurement.
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Estimating the last digit in a measurement
This measurement should be read as 4.95 cm. This
measurement has 3 significant figures.
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Reading a metric ruler correctly
This point can be read as 1.65 cm. or 16.5 mm.
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Reading a metric ruler correctly
This point can be read as 6.70 cm. or 67.0 mm.
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• Mass measurements are made using a balance.
• There are several kinds of balances
• Triple beam balance
• Dial-a-gram balance
• Electronic/ digital balance
• Analytical balance

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The triple beam balance
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The dial-a-gram balance
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The electronic/ digital balance
When using this balance, it is not necessary to
estimate any places.
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The analytical balance
This is used for very technical, precise
applications.
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Mass, in the metric system, is measured in grams
(g.), centigrams (cg.) or milligrams (mg.). 10
mg. 1 cg. (and 1 mg. 0.1 cg.) 100 cg.
1 g. (and 1 cg. 0.01 g.) Also, 1000 g. 1
kilogram (kg.)
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As with all measuring instruments, Sig. Fig.
Rules must be followed when reading a balance.
How would you read this measurement?
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How would you read this measurement?
This should be read as 105.00 grams (g.)
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CHEMISTRY PART DEUX
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COMMON PROCEDURES

• Techniques used
• for various
• Activities

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FILTRATIONPurpose and Definitions

• Used to separate suspensions.
• Filtrate is the liquid portion which passes
  through the filter paper.
• Residue (precipitate) is the portion which
  remains in the paper.

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Procedure

• 1. Fold a circular piece of filter paper into
  quarters to form a cone.
• 2. Insert into a funnel and dampen

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Diluting Acids

• ALWAYS DILUTE
• BY ADDING
• ACID TO WATER
• Do what ya oughta add the acid to the water.

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Constructing Data Tables

• 1. Identify the variables in the experiment.
• 2. Set up tables using appropriate labels and
  state units of measurements.

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Sample Data Table for Melting Pt. Lab.

• Time in sec. Temp.O C
• 0 0
• 5 1
• 10 4
• 15 9
• 20 15
• 25 15
• 30 15
• 35 15
• 40 18
• 45 24

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Graphing

• Label the X and Y axis
• The X axis is the independent variable
• (consistent variable such as time)
• The Y axis is the changing variable

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Temp. C
20
16
12
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4
0
0 5 10 15 20 25 30
35 40 45
Time in Sec.
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20
Temp. C
16
12
8
4
0
0 5 10 15 20 25 30
35 40 45
Time in Sec.
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Temp. C
20
16
12
8
4
0
0 5 10 15 20 25 30
35 40 45
Time in Sec.
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The melting point of this substance is 15 0C as
indicated by the plateau.
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Temp. C
20
16
12
8
4
0
0 5 10 15 20 25 30
35 40 45
Time in Sec.
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Final Review of Specific Labs

• Heating / Cooling Curve
• Density of solids and liquids
• Solubility Curves
• Composition

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HEATING / COOLING CURVE
Plateaus indicate change of phase. Two phases
co-exist
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Liquid-gas
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Gas
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Temp. C
Liquid
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Solid-liquid
16
12
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Solid
4
0
0 5 10 15 20 25 30
35 40 45 50 55 60
Time in Sec.
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Unsaturated 135g _at_ 800C
KNO3 saturated 110g _at_ 600C
Super Saturated 85 g _at_ 400C
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FINIS